A printed circuit board of the type described in the opening paragraph was obtained as a result of research conducted by Applicants. In this printed circuit board each further hole in the solder-stop layer has a round cross-sectional area, the solder section of the second conductor pattern, which is surrounded by such a further hole, exhibiting a ring-shaped cross-sectional area which is commonly referred to as solder land, and the hole in the adhesive layer, which is surrounded by the solder land, and the solder section of the first conductor pattern, which is accessible via this hole for a soldered joint, exhibit a round cross-sectional area, which explains why the latter solder section is commonly referred to as solder pad.
It has been found that due to the difference in shape, round solder sections and ring-shaped solder sections have different soldering properties, for example as regards a uniform distribution of liquid soldering tin exhibiting high surface tensions over all solder sections. Further it has been found that the surface areas of the solder pads and solder lands which can be used for forming soldered joints generally have different dimensions. Besides, further research conducted on such printed circuit boards has revealed that in interconnecting the adhesive layer and the support plate, which is carried out in a pressing process using heat and pressure, the heated and softened adhesive layer is often caused to leak out at the interface between a ring-shaped solder land and the solder pad surrounded by said land, said efflux occurring below the ring-shaped solder land and extending radially towards the solder pad, thereby forming a ring-shaped solder barrier of adhesive material between the solder land and the solder pad, which solder barrier tends to divide the liquid soldering tin; however, due to the high surface tensions of the liquid soldering tin, which counteract such a division, the soldering fin always flows to one side of the solder barrier. Owing to the difference in shape, between the solder lands and the solder pads, which leads to a different soldering behavior, and due to the fact that the dimensions of the surface areas of the solder lands and the solder pads available for forming soldered joint are different, and due to the possible presence of a solder barrier formed by the efflux of adhesive material, relatively often no electrically conductive soldered joints between the solder lands and the solder pads are formed in a soldering process. For example, in a customary industrial wave soldering process, because the still liquid soldering tin is always caused to flow to that one of the two solder sections to be electrically interconnected but exhibiting different shapes and surface areas (and possibly, being separated from each other by a solder barrier, which has the largest surface area) so that the other solder section is only wetted with soldering tin, thereby forming a soldering fin film which is so thin that due to the presence of a solder barrier or a small difference in level between the solder sections to be interconnected, no electrical soldered joint is obtained between the solder sections, i.e. the solder lands and the solder pads. Soldered joints of such poor quality are of course undesirable and disadvantageous because either the printed circuit board must be rejected when the defective soldered joints cannot be traced or the printed circuit board must be subsequently repaired by further soldering processes, which is time-consuming and involves additional costs.